Questions tagged [beam]
Questions about the theory and applications of structural elements designed to resist bending.
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Pin joint system displacement question
A pinned system comprising bars of the same material and cross-sectional area is subjected to a vertical load P.
I am required to form a relationship between FAB and P.
The first part of the ...
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23 views
How to write the equilibrium stress equations for a hollow, rectangular beam?
I have a system consisting of a hollow, rectangular cantilever beam (pictured below). I'd like to write the equilibrium stress equations à la the Cauchy Stress notation.
How do I account for the ...
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1answer
57 views
Why are variations zero on the endpoints of a beam?
On Wikipedia derivation on Timoshenko beam equation we arrive at this:
$$ \delta U = \int_L \left[-M_{xx}\frac{\partial (\delta\varphi)}{\partial x} + Q_{x}\left(-\delta\varphi + \frac{\partial (\...
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1answer
53 views
How to analyze a bent beam: Stress concentration?
I am analyzing a beam, that has a bend in it. Intuitively and inspecting FEA results using a linear solver, there is a stress concentration at the bend of this I-beam.
When I was learning about ...
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1answer
46 views
Calculating area moment of inertia for a beam with underslung plate?
In a number of designs, a beam will have an underslung welded plate attached, as shown below:
In this sketch, a symmetrical standard steel beam/column of dimensions H1 x B1, with web and flange ...
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39 views
Rotational bending in Timoshenko beam theory
The Wikipedia article on Timoshenko beam theory says:
The model takes into account shear deformation and rotational bending effects,
I am familiar with shear deformation, but what is meant by "...
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1answer
38 views
simple supported Beam deflection question involving two point loads and a UDL
so i was given a problem by my mechanical principles teacher to work out the max vertical deflection of a simply supported beam with two point loads one a distance of 5.3 away from A and another 5.9 ...
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1answer
35 views
Along which direction is the area moment of inertia taken in bending moment equation?
Is it in the same direction of the applied load or in the co-planar perpendicular direction to the load applied?
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1answer
37 views
MSC Nastran - BAR3/4 elements - can't assign any properties
I'm modeling a pipe in Patran, and I'd like to try bar3 and bar4 elements.
I assing the properties CBEAM to my geometry, but when I create the mesh, Patran tell me bar3 and bar4 don't support that ...
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3answers
64 views
Do internal / external stresses affect modal frequency?
Imagine a cantilevered beam, fixed on one end and with a tension line connecting the other end to ground (e.g. perpendicular to the length of the beam).
If I increase the tension, does the modal ...
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3answers
73 views
Composite beam- increase in bending moment due to reinforced steel
While trying to solve this question and using the flexure formulas of bending for composite beams I obtained a lower value of moment for steel than for aluminum.How is that possible?
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Reaction Forces on a Beam
I'm new to beams and I'm struggling to find the correct vertical reactions forces at support C and E.
The correct answer is 8.58 kN for $V_c$ and -3.58 kN for $V_e$
However, when I ...
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69 views
How to get the bending moment for tie member?
How to get the bending moment for tie member? For the tie member, there is no uniformly distributed load and concentrated load, right? How to get the bending moment? The tension force was found to be ...
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3answers
80 views
Why does concentrated shear force on a beam influence the whole beam?
This might be a silly question but can someone explain how this shear force on the right side of the beam causes Qy throught the whole beam?
I understand it mathematically but not conceptually so I ...
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0answers
177 views
Simple beam deflection of cantilever beam
Recently I had need to prove the beam deflection equation for a simple cantilever beam with a point load at the end. The equation would be in reference to the Euler-Bernoulli theory taught in most ...
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2answers
196 views
Simple beam with cantilever ends
I'm trying to find the maximum bending moment and deflection for this symmetrical simple beam. The formulae I can find, deal with either cantilever beams with one fixed end, or continuous beams ...
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2answers
146 views
Statically indeterminate fixed-pinned beam problem
F=32KN; Mf1=60KN-m; Mf2=-58KN-m; g=30KN/m I need to solve this using Force method. Find the reaction at the pinned end.
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2answers
463 views
Stiffness of a cantilever beam
I am working on calculating the stiffness of a cantilever beam by applying a distributed load. I wanted to ask if the distribution of the load on the beam effects its stiffness.
For eg., if I apply a ...
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1answer
104 views
Can bending moments for a combination of loads on a simple beam, be calculated by adding the individual B.M. of each load?
This problem is about bending moment of a simple beam subject to a mixture of 4 or 5 UDLs and point loads. The beam is assumed to be rigid enough that deflection of the combined load is "small".
...
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2answers
94 views
Indeterminate beam with a guide at each end
I've been battling with a statics question (as attached) and can't for the life of me figure it out.
I've attempted removing the left side guide joint so then there are only 3 reactions and it should ...
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2answers
180 views
Shear force and bending moment for continuous span
It's given that L1 = 5m, L2 and L3= 7.5m, w = 8.9kN/m , I am asked to find the bending moment using these coefficient.. Prior to this , i need to have the value of shear force first.Shear force = ...
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37 views
Possible improved approaches to 6mx3m moment-resisting frame with eccentricity+torsion, in advance of detailed engineer discussion
I'm putting a steel frame in, to "open plan" the rear of a brick cavity-wall terrace house in the UK, which will then have a single storey extension added behind it.
I have already retained a ...
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1answer
161 views
Shape Functions of beam element with 3 nodes (quadratic element)
For a two node beam element there are four shape functions for four degree of freedom:
For a straight three node beam element how shape functions are?
Please note that beam is straight and not ...
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1answer
29 views
Big Beam LVL or Glu Lam load capacity to support a gymnast
I need help knowing if I am selecting the correct wood beam.
The load will be all near the center and a 250 pound man will be doing pull ups on it. I would estimate a 1,000 pound dynamic load to be ...
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59 views
What is the optimal shape of a beam subject to three point bending?
Assume we have a beam with density $\rho$ that is subject to three-point bending according to the image above. The beam cross section is rectangular with the variable height $H(x)$ and constant width $...
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1answer
52 views
Calculation of natural frequency in a hinged beam
What I tried: Using the conjugate beam method to find deflection and hence stiffness of the beam, but I am unable to find reactions in the conjugate beam.
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189 views
Derivation of Bimetallic Strip Stress in Roark's Formulas
I am trying to understand some analytic expressions given in the handbook Roark's Formulas for Stress and Strain for bimetallic strip stresses. Namely, Roark's Formulas give the formulas
$$\text{...
3
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1answer
120 views
Torsional rigidity D vs torsional rigidity factor k vs torsion constant J
I have a physics background so apologize my ignorance.
I'm confused by the constants $D$, $\kappa$, and $J$ when it comes to torsion of beams. From what I understand $\kappa$ and $J$ are the same ...
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1answer
18 views
Supporting flexible square plate of uniform density in equilibrium with only 4 rolling contacts placed along the square's diagonals
Consider a flexible square of uniform density with vertices (0,0), (0,1), (1,0), (1,1). I need the 4 coordinates for rolling contacts along the diagonals that will stably support it. Someone could ...
3
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1answer
141 views
How to measure the unbraced length of lateral torsional buckling for negative moment in a W-shape steel beam?
I have a W-shape steel beam that is fixed-fixed and the top flange is fully braced for lateral torsional buckling. The negative moment at the end controls the design and there is no lateral bracing ...
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4answers
452 views
How does stiffness/rigidity affect the bending moment of a beam
My question may sound silly as it’s mainly good sense but I may be mixing things up.
Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other ...
2
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2answers
69 views
Why two identical beams without being pinned together will share half of the bending moments?
As shown above, two identical rectangular beams are placed and NO pinned together. I know each beam has its own neutral surface but why they carry half of the bending moments? I thought the bending ...
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1answer
37 views
What's the second moment of a T beam with a heel? [closed]
The second moment of area of a rectangle is $I_{yy} = \dfrac{bh^2}{12}$
b : base
h : height
What is the second moment of area of a T beam like this one?
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50 views
How much (uniformly distributed) weight can this L beam support without bending? [closed]
As you can see in the picture, the L beam is 1in x 1/2in x 1/8in thick x 72in long and is made of ASTM A36 steel. It's bolted onto a vertical upright on both ends.
What is the maximum uniformly ...
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1answer
63 views
Abaqus Failure for I-Beam Section in Major direction only
For my 4th year dissertation in Civil Engineering I've got to investigate the difference between BS5950, Eurocode 3 and ABAQUS failures. The only thing is, in the BS5950 and Eurocode 3 the failure can ...
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2answers
87 views
Resulting torque on the cross section
I have trouble solving part A of the question. I thought the resulting torque would just be 10k * L of the beam.
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1answer
59 views
Which container orientation, if any, can hold more weight?
These are cross sections of identical shipping containers, except one is rotated 45 degrees. The cross sections are squares, 3 meters to a side. I drew dashed lines to show where they're suspended by ...
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2answers
146 views
Neutral axis in canteliver beam at support
First, I thought the neutral axis would just be the y bar which can be obtained from the centroid of the cross-section but is different. I have tried letting the net moment at the wall = 0 and the ...
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1answer
107 views
Should one use multiple elements through the thickness with multiple materials?
To get realistic results from a FEM calculation, it is common (or so I've been taught by someone who may not be up to date) to use at least four or five elements through the thickness of a beam or ...
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172 views
How to add Beam cross section properties to imported mesh in Ansys?
Ansys Workbench 17.1
I have a mesh that was imported from Abaqus into Ansys but the beam cross section data is missing. As a result the structural model omits the beam elements.
How do I access the ...
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2answers
392 views
Deflection of a cantilever beam composed of separate (not bonded) planks
In the case of a simple cantilever beam having a uniform shape and being loaded at its end - the calculation of the deflection at any point along the beam is well known.
What happens if we split it ...
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2answers
103 views
Is is possible to use singularity function to expresse the horizontal forces ?
I know how to translate torques and vertical forces into singularity functions, but may i also express the horizontal forces with singular function? if yes then what would be that expression?
Here ...
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1answer
77 views
Shear forces along a beam using singularity functions
$\newcommand{\a}[1]{\langle#1\rangle}$
As you can see, the left end of the beam is fixed, and a distributed load is applied to the beam. I calculated the shear forces by conventional means, but when I ...
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1answer
268 views
Bending equation and max deflection of UDL and multiple point loads
I have a beam, simply supported with 2 points loads and 2 UDLs. The loads are symmetric about the centre of the beam.
I've tried to derive an expression for the moment along the beam and then via 2 ...
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2answers
54 views
Loadcell / strain gauge sizing for a joist
I am looking to use some load cells (foil based type) to detect presence for home automation within in a room. I was looking to mount some loadcells to the joists for the floor (UK Based house so ...
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2answers
713 views
What exactly is the thin wall assumption in regards to beam cross sections?
What does it mean with respect to calculating stresses on a beam undergoing loading and when should it be applied?
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1answer
195 views
Timoshenko Beam Theory for Quasistatic Cantilever Beam: Shear Term
I'm trying to determine the effect of shearing force on the deflection of a quasistatic cantilever beam. In his book, Theory of Elasticity, Timoshenko added the following term to the deflection:
$$\...
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2answers
49 views
How to find a beam for my (simple) application
I have a spanof 9m that I bridge with a (as yet unspecified) beam. From this beam hangs a load (a pipeline), right in the middle, of 4.295 kN. The beam is simply supported. I want to use an IPE steel ...
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2answers
842 views
Ceiling mounted punching bag without compromising structure or floor above
This question is regarding the safest way of installing a heavy punching bag of 100 lbs from the basement ceiling. Above the basement ceiling is a wood floor. The goal is to sleep soundly at night ...
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1answer
73 views
How does the superposition principle relate to Bernoulli-Euler and Timoshenko beam theory? [closed]
I have a shaft with a bearing in each end, and a large eccentric mass covering the entire "free length" of the shaft.
The attachment of the eccentric mass is done using heat shrinking.
Without ...
